Antibodies are provided which specifically bind human and Macaca fascicularis lysosomal-associated membrane protein 1 (LAMP1) proteins and immunoconjugates comprising said antibodies conjugated or linked to a growth inhibitory agent. Pharmaceutical compositions comprising antibodies or immunoconjugates of the invention and use of the antibodies or immunoconjugates for the treatment of cancer are also provided, as well as LAMP1 antibodies, isolated nucleic acids, vectors and host cells comprising a sequence encoding said antibodies and the use of said antibody as a diagnostic tool. The application further provides for the detection of LAMP1 gene amplification or gain in cancer cells leading to the determination if patients with cancer are likely to respond to anti-LAMP1 therapy. Therefore, it is proposed an in vitro method of selecting patients with cancer which comprises determining, in a biological sample of a patient with cancer which includes cancer cells, if said patient harbors a LAMP1 gene copy number gain; and selecting the patient based on the presence of LAMP1 gene copy number gain. Anti-LAMP1 therapeutic agent for use for treating cancer in a patient harboring LAMP1 gene copy number gain in cancer cells is further provided.
Lysosome-associated membrane protein 1 (LAMP1), also known as CD107 antigen-like family member A (CD107a), is a single-pass type I membrane protein, which belongs to the LAMP family. LAMP2 is the closest member of the family and both proteins are the most abundant glycoproteins within the lysosomal membrane (Sawada, R. et al., 1993, J Biol Chem 268: 12675-12681).
Although encoded by separate genes, with LAMP1 located on chromosome 13q34 and LAMP2 on Xq24-25, the proteins are similar in their primary structure, with ˜36% sequence homology (Mattei, M. G. et al., 1990, J Biol Chem 265:7548-7551). LAMP1 and LAMP2 consist of a polypeptide core of approximately 40 kDa; they are both anchored via their C-terminus to the lysosomal membrane and expose the largest part, extensively glycosylated, to the lumenal side of lysosomes. Both proteins are among the most heavily glycosylated of cellular proteins with ˜50% of their mass as carbohydrates and these glycosylations seem to be the key for maintaining lysosome acidity and protecting the lysosomal membranes from autodigestion. However, the full biological function of these two highly glycosylated proteins in particular LAMP1 still needs to be elucidated (Fukuda, M., 1991, J Biol Chem, 266:21327-21330; Winchester, B., 2001, European Journal of Paediatry Neurology, 5:11-19; Gasnier, B., 2009 Biochimica et Biophysica Acta 1793:636-649).
LAMP1 is highly expressed in late endosomes and lysosomes designating LAMP1 as marker for these two organelles (Cook, N. R. et al., 2004, Traffic, 5 (9): 685-699). Thus, most of the literature on LAMP1 relates to endocytosis, pinoscyosis, or phagocytosis (Cook, N. R. et al., 2004, Traffic, 5 (9): 685-699).
Although the majority of LAMP1 and LAMP2 reside in the lysosome, some LAMP1 and LAMP2 immunoreactivity is also observed at low levels at the plasma membrane. The LAMP1 found in the plasma membrane represents only 1-2% of total LAMP1. This is for example true for peripheral blood lymphocytes (Holcombe, R. F. et al. 1993, Clin Immunol Immunopathol. 67(1): 31-39) and platelets (Silverstein, R. L. and Febbraio, M., 1992, Blood 80: 1470-1475).
Increased cell surface expression of LAMP1 and LAMP2 has been observed in tumor cell lines, for example in highly metastatic colonic carcinoma L4 cells (Saitoh, O. et al., 1992, J Biol Chem 267: 5700-5711), on human metastasizing melanoma A2058, HT1080 (human fibrosarcoma), CaCo-2 (human colon-adenocarcinoma) cells and in colorectal neoplasms (Furuta, K. et al., 2001, J Pathol 159 (2): 449-455).
The chromosomal region 13q34 in which LAMP1 is located has recently been linked to amplification events including a larger amplicon that involves CUL4A, LAMP1, TFDP1, and GAS6 in human breast cancer (Abba, Martin C. et al.; Cancer Res 2007; 4104). TFDP1 and perhaps CUL4A were identified in the above mentioned publication as the leading genes driving the amplification phenomenon. In particular, analysis of publicly available breast cancer gene expression (microarrays) data sets indicated that TFDP1 overexpression is associated with estrogen receptor (ER)-negative and high-grade breast carcinomas, as well as shorter overall survival, relapse-free survival, and metastasis-free interval. Conversely, LAMP1 expression did not significantly correlate with tumor grade. In the end, Abba et al. did not report that LAMP1 amplification translated into LAMP1 overexpression in human breast cancer cells.
The 11 amino-acid cytoplasmic tail of LAMP1 contains a 7 amino-acid linker sequence and a 4 amino acid long tyrosine motif (YQTI). It was shown that small changes in the spacing of this motif relative to the membrane dramatically impair sorting in the early/sorting endosomes. Mutations within said tyrosine motif were shown to have an impact on the binding of LAMP1 to adaptor proteins leading as well to impaired sorting (Obermuller, S. et al., 2002, Journal of Cell Science 115: 185-194; Rohrer, J. et al., 1996, Journal of Cell Biology 132(4): 565-576). Therefore, the abnormal cell surface expression of LAMP1 in different cancer cell lines might be related to mutations in the cytoplasmic tail even though the mechanism is still unclear. Furthermore, it has been shown that certain point mutations in the cytoplasmic tail lead to plasma membrane accumulation (Gough, N. R. et al., 1999, Journal of Cell Science 112 (23): 4257-4269).
Due to the fact that LAMP1 is a marker for endosomes and lysosomes, numerous commercially available anti-LAMP1 antibodies were developed for research purposes. These antibodies are either polyclonal or monoclonal and are restricted to some biochemical application such as immunohistochemistry (IHC), Western blots (WB), Fluorescence activated cell sorter (FACS) analysis, Immunoprecipitation (IP) and Enzyme-linked immunosorbent assay (ELISA).
LAMP1 protein also has been detected at the cell membrane of tumor cells.
E. Venetsanakos (WO 2005/012912) suggested that LAMP1 is expressed on the surface of colon cancer cells but not on the surface of normal colon cells and proposed that tumor growth might be reduced by targeting a cytotoxic agent to LAMP1 via an anti-LAMP1 antibody. Venetsanakos did not describe, however, preparation of anti-LAMP1 antibodies or conjugates thereof with cytotoxic or cytostatic agent or any data supporting his hypothesis. Indeed, though a decade has passed since Venetsanakos' initial filing and no anti-LAMP1 antibodies or their use as immunoconjugates in an anti-LAMP1 therapy has entered clinical development, so far. Accordingly, a great need exists for anti-LAMP1 antibodies or immunoconjugates for the treatment of cancer.